A botanical name is a formal scientific name conforming to the International Code of Botanical Nomenclature (ICBN) and, if the plant is a cultigen, the additional cultivar and/or Group epithets must conform to the International Code of Nomenclature for Cultivated Plants (ICNCP). The purpose of a formal name is to have a single name that is accepted and used worldwide for a particular plant or plant group. For example, the botanical name Bellis perennis is used worldwide for a plant species, which is native to and has a history of many centuries use in most of the countries of Europe and the Middle East, where it has accumulated various names in the many languages of that area. Later it has been introduced worldwide, bringing it into contact with languages on all continents. The cultivar Bellisperennis 'Aucubifolia' is a golden-variegated horticultural selection of this species. English names for this plant species include: daisy, common daisy, lawndaisy, etc.

The usefulness of botanical names is limited by the fact that taxonomic groups are not fixed in size; a taxon may have a varying circumscription. The group that a particular botanical name refers to can be quite small according to some people and quite big according to others.
This will depend on taxonomic viewpoint or taxonomic system. The traditional view of the family Malvaceae includes over a thousand species, but in some modern approaches it contains over four thousand species. The botanical name itself is fixed by a type, the size and placement of the taxon it applies to is set by a taxonomist. Some botanical names refer to groups that are very stable (for example Equisetaceae, Magnoliaceae) while for other names a careful check is needed to see which circumscription is being used (for example Fabaceae, Scrophulariaceae, Urticaceae, etc).

Depending on rank, botanical names may be in one part (genus and above), two parts (species and above, but below the rank of genus) or three parts (below the rank of species):in one part Plantae (the plants) Marchantiophyta (the liverworts) Magnoliopsida (class including the family Magnoliaceae) Liliidae (subclass including the family Liliaceae) Pinophyta (the conifers) Fagaceae (the beech family) Betula (the birch genus)

A name in three parts, i.e. the name of an infraspecific taxon (below the rank of species) needs a "connecting term" to indicate rank. In the Calystegia example above, this is "subsp." (for subspecies). In botany there are many ranks below that of species (in zoology there is only one such rank, subspecies, so that this "connecting term" is unnecessary there). A name of a "subdivision of a genus" also needs a connecting term (in the Acacia example above, this is "subg.", subgenus). The connecting term is not part of the name itself.

A taxon may be indicated by a listing in more than three parts: "Saxifraga aizoon var. aizoon subvar. brevifolia f. multicaulis subf. surculosa Engl. & Irmsch." but this is a classification, not a formal botanical name. The botanical name is Saxifragaaizoon subf. surculosa Engl. & Irmsch. (ICBN). Generic, specific, and infraspecific botanical names are usually printed in italics. The example set by the ICBN is to italicize all botanical names, including those above genus, though the ICBN preface states: "The Code sets no binding standard in this respect, as typography is a matter of editorial style and tradition not of nomenclature". Most peer-reviewed scientific botanical publications do not italicize names above the rank of genus, and non-botanical scientific publications do not, which is in keeping with two of the three other kinds of scientific name; zoological and bacterial (viral names above genus are italicized, a new policy adopted in the early 1990s).

Binary name

For botanical nomenclature, the ICBN prescribes a two-part name or binary name for any taxon below the rank of genus down to, and including the rank of species. Taxa below the rank of species (infraspecific taxa) get a three part name (ternary name).
The ranks explicitly mentioned in the ICBN as having a binary name are:

subgenus

section

subsection

series

subseries

species

A binary name consists of the name of a genus and an epithet.

In the case of a species this is a specific epithet: Bellisperennis is the name of a species, with perennis the specific epithet. There is no connecting term involved, to indicate the rank

In the case of a subdivion of a genus (subgenus, section, subsection, series, subseries, etc) the name consists of the name of a genus and a subdivisional epithet. A connecting term should be placed before the subdivisional epithet to indicate the rank.

More than two parts

In the case of a cultivar there is an additional cultivar epithet (this is a non-Latin part of the botanical name and is not written in italics). The cultivar epithet may follow either the botanical name of the species, or the name of the genus only, or the common name of the genus or species (provided the common name is unambiguous). The generic name, followed by the cultivar name, is often used when the parentage of a particular hybrid cultivar is uncertain or when it cannot be linked with certainty to a particular species. Bellisperennis is the name of a species, with perennis the specific epithet and 'Aucubifolia' the cultivar epithet.

Sometimes a subdivision of a genus may be indicated with a listing in three or more parts. However, this is not its formal name. Its botanical name is in two parts.

Understanding the System of Botanical Plant Names

When talking with some members of the Australian Plants Society recently, the subject of understanding botanical names came up.

Their question was "What do all these names really mean ? "

To anyone who is new to plants, these botanical names can be very confusing, and difficult to pronounce and to remember. Just using the common name instead can lead to more confusion. You may use a common name to refer to one plant, while I may only know it by a different common name. By using the botanical name, we both know what plant is being discussed.

A good example of common name confusion is the eucalypt with the common name of Blue Gum. Now, do you mean the Sydney Blue Gum, the Victorian Blue Gum, the Tasmanian Blue Gum, or one of the dozen or so other eucalypts with the common name of Blue Gum. These are all different species, and only by using the botanical name can we be sure what we are talking about.

It seems as if the botanical names are always changing. This is because in the botanical world of plant naming, it is the person who first published a name and a description for a new plant who has the right to give the "correct" name to the plant.

Back in the days when Australian plants were being discovered by Europeans (Aborigines had discovered, named and found uses for these plants hundreds, perhaps thousands of years earlier), there was a lot of confusion. A huge amount of material was collected and most of it was sent back to England and Europe for identification. The long time delay in this process caused confusion, especially at a time when there was some prestige in being the first to name a new plant. Inevitably, mistakes were made.

In the mid-1980s, the Australian Government determined that all of the Australian flora was to be checked for identification correctness. The results have been published in a series of monumental books entitled "The Flora of Australia". This has been a massive ongoing project.

The Naming System in Botanical name

In 1753, Carl von Linne (= Linnaeus in Latin), a Swedish botanist, published a system of scientific plant names involving two parts. This system has been used world-wide since that time. The first name, always spelled with a capital first letter, is the genus or generic name. It may be in honour of a person, eg. Banksia after Sir Joseph Banks, or in reference to characteristics of the plant, eg. Callistemon. meaning "beautiful stamens" (Greek kallistos = "beautiful"). The second name (always spelled with a small first letter) is the species name, and may honour a person, or describe a feature of the plant, or identify the geographic region where it grows.

I liken the naming of plants to our own system of first name and surname, except that with plants, the names are in reverse, with the "surname" or genus name first, eg. Banksia, and with the "Christian name" or species name second, eg. ericifolia. Sometimes, an extra name is added, eg. Banksia ericifolia var. macrantha. The "var". is short for "variety", meaning there are taxonomic differences that make it distinct from the rest of the species.

At other times, we come across plant names with a genus name, eg. Viola, a species name, hederacea, and the extra name ssp. sieberiana. "ssp" or "sub-species" means there are differences in minor morphological character, such as in size or shape of the parts, due to growing in partial or complete isolation because of geographical or ecological barriers.

Let's illustrate this naming system by looking at some of the plants that grow on the Central Coast of New South Wales. The following list is a small sample, enough to illustrate the principles behind the apparently complex system of naming plants.

Genus

Species Examples

Actinotus
- From Greek actinos = like the spokes of a wheel, referring to the spreading bracts.

helianthi = similar to the genus Helianthus, the sunflower (common name "Flannel Flower)

ericifolia = having leaves like the genus Erica.robur = having leaves like the English oak-tree Quercus robur.spinulosa = bearing small spines.marginata = with a margin round the edge of the leaves.integrifolia = with leaves "entire", ie. not toothed or indented.

Blandfordia
- After George Spencer Churchill, Marquis of Blandford, 19th century flower lover.

grandiflora = having large flowers (common name "Christmas Bells").

Boronia
- After Francesco Borone, 18th century Italian botanist.

ledifolia = with leaves resembling the genus Ledum.serrulata = with fine teeth along the margin of the leaves (cf "serrated").

Brachyloma
- From Greek brachys = short and loma = edge or fringe. This alludes to the hairs or scales in the throat of the corolla tube.